There have been some efforts in the art to control the problem of uniformity over a multiple element compound semiconductor surface when an ion implantation annealing step is employed.
The tendency of the multiple element compound semiconductor GaAs to decompose during processing has received some attention in the art. There have been two general techniques employed. The first is by applying a capping layer, such as SiO.sub.2, which prevents decomposition. This first technique is shown in U.S. Pat. No. 4,226,667.
The second technique involves the use of a native oxide of the GaAs and this technique is illustrated in U.S. Pat. No. 3,969,164.
The art has principally been directed to a control of surface stoichiometry. In U.S. Pat. No. 4,135,952 an effort is made to keep GaAs from decomposing during ion implantation annealing by placing the GaAs crystal surface in proximity with a GaAs crystal in a Ga solution. The desirability of having an excess of the more volatile element of the GaAs is shown in U.S. Pat. No. 4,312,681 wherein InAs is used as a source of excess arsenic to prevent decomposition. Each of these require a standard long, about 30 minute, annealing step.
In Appl. Phys. Lett. 38, 8 15 Apr. 1981, p. 639, detrimental effects of diffusion of certain substrate impurities in the material GaAs during long annealing steps is recognized and high excess As pressure from InAs is employed for control.
In Device Research Conference IVA-7-June 26-28, 1982, selective evaporation of GaAs during a conventional long ion implantation annealing step and diffusion of Mn from substrate are reported as problems.